The present invention relates to a method of making a magnetic resistance element, which is employed in a magnetic head of a magnetic disc drive unit, etc.
The magnetic resistance element is capable of detecting a magnetic field by the magnetic resistance effect, and it is employed in the magnetic head of the magnetic disc drive unit, which is capable of reading high density data from a magnetic disc. These days, the disc drive units are made smaller in size but they have large capacity of memory, further high power magnetic heads are required, so the magnetic resistance elements, in which magnetic domains are controlled by ferromagnetic layers, draw engineers' attention.
The magnetic resistance element, in which the magnetic domains are controlled by the ferromagnetic layers, is shown in FIG. 6. An insulating layer 10 is made of an insulator, e.g., alumina, silicon oxide. A first magnetizable layer 12 is formed on the insulating layer 10; a non-magnetizable layer 14 is formed on the first magnetizable layer 12; and a second magnetizable layer 16 is formed on the non-magnetizable layer 14. One of the first and the second magnetizable layers 12 and 16 is a magnetic resistance layer (MR layer), and the other is a bias layer (SAL layer). The SAl layer applies a bias magnetic field to the MR layer so as to detect magnetic data with high sensivity. The non-magnetizable layer 14 is provided between the first and the second magnetizable layers 12 and 16 as a shielding layer. A Ni--Fe layer is employed as the MR layer; an alloy layer, which is made of two or more selected from a group of Ni, Fe, Cr, Rh, Co, etc., is employed as the SAL layer; and a layer made of Ta, Ti or Cr is employed as the non-magnetizable layer.
Planar shapes of the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 are rectangular shapes; their side faces are formed into slope faces on which terminals 18 are formed; and they constitute a main part of the magnetic resistance element. The terminals 18 are formed on the slope faces of the main part. Since the terminals 18 are formed on the slope faces, the contact area between the terminals 18 and the first and the second magnetizable layers 12 and 16 can be broader, so that the resistance of the magnetic resistance element can be reduced.
A conventional method of making the magnetic resistance element is shown in FIGS. 7A-7C. In FIG. 7A, the insulating layer 10, the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 are formed on a substrate, e.g., a ceramic member. The layers can be formed, in said order, by sputtering.
As shown in FIG. 6, in the case of the magnetic resistance element of the magnetic head, etc., the terminals 18 are formed on the side slope faces. Thus, a resist layer 20, which is formed into a prescribed shape, is formed on an upper face of the second magnetizable layer 16, which is the uppermost layer as a mask, then the layers are etched, with the mask of the resist layer 20, by ion milling, as shown in FIG. 7A.
In FIG. 7B, the slope faces, on which the terminals 18 FIG. C are formed, are formed in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling. A sectional shape of the resist layer 20 has undercut sections, namely a wider section 20a is supported by a supporting section 20b, which is narrower than the wider section 20a. When ions are radiated by ion milling, the slope faces for the terminals 18 are formed by partially shading the ion radiation by the wider section 20a; the terminals 18 can be formed on each slope face.
To form the slope faces in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling, they are gradually etched from the second magnetizable layer 16 toward the lower layers. In an are alocated outside of the slope faces on which the terminals 18 are formed, the insulating layer 10 is exposed, so the surface of the insulating layer 10 is slightly overetched, by ion milling, so as to leave no layers on the insulating layer 10. In FIG. 7B, a symbol "L" stands for depth of overetching the insulating layer 10.
In the conventional method, to correctly etch the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling, the etching is stopped on the basis of the operator's visual observation or on the basis of the time required to completely remove the first magnetizable layer 12, which has been previously known. Therefore, overetching of the insulating layer 10 cannot be avoided so as to completely remove the first magnetizable layer 12 from the surface of the insulating layer 10.
If the insulating layer 10 is overetched after the slope faces are formed in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16, the insulating materials of the insulating layer 10 are scattered and stick onto the slope faces, on which the terminals 18 are formed. In FIG. 7C, the insulating materials 10a of the insulating layer 10 stick on the slope faces, and the terminals 18 are formed thereon.
If the terminals 18 are formed on the slope faces on which the materials 10a have stuck, the magnetic resistance element has the following disadvantages: the resistance between the terminals 18 and the main part is unstable; and therefore the resistance of the magnetic resistance element must be greater.
Further, the first and the second magnetizable layers are heated while forming on the insulating layer 10, atoms of the first magnetizable layer 12 are spread in the insulating layer 10, so that magnetic characteristic of the magnetic resistance element must be worse. In the case that the first magnetizable layer 12 is the SAL layer, if the atoms of the first magnetizable layer 12 are spread in the insulating layer 10, the magnetic characteristic of the first magnetizable layer 12 is changed, and a prescribed bias magnetic field cannot be applied.